import math


class Counter:


    @staticmethod
    def add(a,b):
        c=a+b
        return c

    @staticmethod
    def jian(a,b):
        c=a-b
        return c

    @staticmethod
    def cheng(a,b):
        c=a*b
        return c

    @staticmethod
    def chu(a,b):
        if b==0:
            raise ValueError("除数不能为0")
        return a / b
    @staticmethod
    def sqrt1(a):
        if a <0:
            raise ValueError("参数不能小于0")
        return math.sqrt(a)

def test1():
    try:
        print(Counter.add(1, 3))
        print(Counter.jian(3, 4))
        print(Counter.cheng(2, 3))
        print(Counter.chu(3, 1.5))
        print(Counter.sqrt1(9))
    except ValueError as e:
        print(e)
    try:
        print(Counter.chu(3,0))
    except ValueError as e:
        print(e)
    try:
        print(Counter.sqrt1(-9))
    except ValueError as e:
        print(e)
test1()